This invention relates to an apparatus and method for creating film applications of a multi-version type and generating bitstream for seamless reproduction to be stored in optical discs, and a recording medium storing program run on the apparatus.
DVD (Digital Video Disc) sits in the strongest limelight of late among mediums for recording video works, such as films. About three hours of video information can be stored in one DVD. It is considered that the most suitable applications for DVD are film applications of multi-version types in which a plurality of video versions are managed together.
The film application of the multi-version type described here includes various versions, which have partially different video or audio data, of the same film. The various versions include, for example, versions with a viewing limitation differently imposed on adults and children, versions with different camera angles, versions for theaters, and versions for TV broadcasting. When viewing such a film application, the users can select a desired version based on their tastes or circumstances at home. This kind of film supply serves the interests of users, enabling the users to select a desired version at their discretion.
It is expected that such film applications of the multi-version type would be appreciated by the customer. However, creating such film applications is not so easy. The producer is expected to make enormous efforts which they have never experienced. In the DVD standard, video data is encoded under MPEG2 (ISO13818), where MPEG is short for Moving Picture Expert Group. The encoding of the video materials under MPEG2 goes through a first path and a second path. In the first path, characteristics are extracted from images every about 0.5 seconds, and parameters (e.g., quantization width) used for the compression are determined. In the second path, the video data is compressed using the determined parameters. This two-path system secures the high quality of the created film applications. On the contrary, it takes more than double the reproduction time of the film to encode corresponding video data. Furthermore, the time taken for the encoding increases proportional to the number of the versions of a film to be encoded. This puts a heavy load on the producer.
The DVD standard defines an exclusive reproduction function for the disc reproduction apparatus to prevent the encode time from increasing. By using the exclusive reproduction function, the disc reproduction apparatus can selectively reproduce video data as specified by the user. With this function, the entire video data for each version need not be encoded, but only different parts of video data are encoded. The exclusive reproduction function is described below with reference to FIGS. 1, 2A, and 2B.
FIG. 1 shows two versions A and B recorded in a DVD. Each rectangle in the drawing represents an image. The width of each rectangle is proportionate to the image reproduction time. FIG. 1 indicates that either of images 2 and 3 is selected and reproduced in the exclusive reproduction. Image 3, shorter than image 4, is a part of image 4. In version A, video data is reproduced in the order of images 1, 2, and 4. In version B, video data is reproduced in the order of images 1, 3, and 4.
FIG. 2A shows a layout of DVD storing the images 1-4. The present drawing shows that each of the images 1-4 is recorded in consecutive sectors of the disc.
In addition to the images, the DVD shown in FIG. 2A stores reproduction route data set which indicates the reproduction order of the images.
FIG. 2B shows the contents of the reproduction route data set. The present drawing includes reproduction route data 1 and 2 which respectively indicate the reproduction orders of versions A and B. The disc reproduction apparatus performs the exclusive reproduction by reproducing the images of each version in accordance with the reproduction orders shown in FIG. 2B.
As described above, when the disc reproduction apparatus uses the exclusive reproduction function, video data need not be encoded for each version. On the other hand, the exclusive reproduction is accompanied by disc seeks of a large scale. Large-scale disc seeks stop the reading of data from the disc, reduce the rate of displaying image, and generate such big gaps as can be detected with naked eyes in the displayed images while the images should be displayed continuously.
The disc reproduction apparatus under the DVD standard uses a seamless reproduction method to prevent the gaps between display images by disc seeks. Basically, for the seamless reproduction, the disc reproduction apparatus is provided with a track buffer in which data is temporarily stored. During disc seeks, the data stored in the track buffer is transferred to the decoder for video reproduction to secure video reproduction without gaps.
For the seamless reproduction by the disc reproduction apparatus, the address of each image on the disc is determined in consideration of the capacity of the track buffer. For example, to prevent the occurrence of gaps between images 1 and 2, images 1 and 3, images 2 and 4, and images 3 and 4, the addresses of the images 1-4 are determined so that each distance between each pair of images is adjusted in accordance with the capacity of the track buffer.
For achieving the seamless reproduction, it is also important to prevent disorder of synchronization from occurring in the video or audio reproduction and to prevent reduction in the display rate which would occur when video is synchronized with audio.
The video and audio data are encoded and interleaved into optical discs, the video data being encoded with the MPEG method. The interleaving process introduced in the present document generates digital data by alternately arranging 2 KB-audio and 2 KB-video components. The generated digital data is called a system stream in general. In the DVD standard, it is called a video object. An arrangement of the audio and video components based on a certain rule is called an interleave structure.
According to general interleave structures of system streams, the audio and video components are alternately arranged. However, to prevent the synchronization disorder and the reduction in the display rate, the interleave structure should be made special.
That is to say, each system stream should have dependent relation between the preceding and succeeding system streams. For example, an audio component which should be included in the preceding system stream is included in the succeeding system stream.
One problem in the above method is that the reproduction order of the system streams should be determined in advance. Also, a once-determined reproduction order cannot be changed.
As a result, when the producer of a film application has an urge to partially amend once-combined system streams from the viewpoint of total design, the producer need to perform the whole processes of encoding and interleaving the video data.
A typical amendment from the viewpoint of total design is to cut or replace system streams corresponding to a scene when the size of the system streams exceed the capacity of DVD.
It will take an enormous time before a whole film application has been created for shipment if the encoding process is repeated each time a trivial error is found from the viewpoint of total design. This renders the production of a film application of the multi-version type unrealistic.
It is therefore an object of the present invention to provide an apparatus and method for creating film applications of a multi-version type in which video data need not be encoded due to minor corrections such as cutting or replacing system streams corresponding to one scene, and a recording medium storing program run on the apparatus.
The above object is achieved by a bitstream generation apparatus for generating a bitstream including a plurality of video objects to be stored in an information recording disc, the bitstream generation apparatus comprising: a video encoder for encoding a plurality of pieces of input video information to obtain a plurality of pieces of video data; an audio encoder for encoding a plurality of pieces of input audio information to obtain a plurality of pieces of audio data; a recording means for recording the plurality of pieces of video data and the plurality of pieces of audio data; a structure information receiving means for receiving structure information which shows correspondence between each of the plurality of video objects and each piece of video data and each piece of audio data recorded in the recording means; an editing means for editing reproduction route information in accordance with an instruction from an operator, the reproduction route information indicating a reproduction order of the plurality of video objects when the information recording disc is reproduced by a reproduction apparatus; a correcting means for correcting each piece of audio data corresponding to each of the plurality of video objects in accordance with a limitation imposed on each of the plurality of video objects dependent on the reproduction order indicated by the reproduction route information, the correspondence being shown in the structure information; an interleaving means for dividing each of the corrected pieces of audio data and the plurality of pieces of video data into blocks and interleaving the blocks to obtain the plurality of video objects by arranging the blocks in accordance with a predetermined rule; and a generating means for generating the bitstream from the plurality of video objects and the reproduction route information.
With the above construction, after corrections such as cutting or replacing system streams corresponding to one scene are performed, the correcting means corrects each piece of audio data corresponding to each of the plurality of video objects in accordance with a limitation imposed on each of the plurality of video objects dependent on the reproduction order indicated by the reproduction route information. By interleaving the above-corrected audio data, each of the generated system streams have dependent relation between the preceding and succeeding system streams. With this arrangement, the reproduction order of the system streams can be changed as desired.
The bitstream can be generated reelecting the above correction without encoding the video and audio information.
With this arrangement, it takes a short time before a whole film application has been created by repeating partial modifications and deletions of video data from the viewpoint of total design. This renders the production of a film application of the multi-version type realistic for producers.
In the above bitstream generation apparatus, the limitation imposed on each of the plurality of video objects dependent on the reproduction order may be a limitation required to allow the reproduction apparatus to change, in reproduction, from one video object to a next video object with a predetermined display rate, wherein the correcting means includes: a first correcting unit for cutting one or more blocks located at the end of a piece of audio data corresponding to a video object and adding the cut blocks to the start of another piece of audio data which corresponds to a next video object.
With the above arrangement, the first correcting unit cuts blocks located at the end of a piece of audio data corresponding to a video object and adds the cut blocks to the start of another piece of audio data which corresponds to a next video object, each time the reproduction route information is edited. This performs a process for preventing the reproduction of video data from delaying. As a result, even if the reproduction route information is edited many times, the reproduction of video data is not delayed and the seamless reproduction is achieved.
In the above bitstream generation apparatus, the reproduction route information may include specification information specifying the video object and link information of the next video object, the editing means may include a link unit for setting the specification information and the link information into the reproduction route information, and the correcting means may include a second correcting unit for cutting one or more blocks located at the end of a piece of audio data corresponding to a link source video object which links to a plurality of link destination video objects and adding the cut blocks to the start of other pieces of audio data which correspond to the plurality of link destination video objects.
With the above arrangement, the second correcting unit cuts blocks located at the end of a piece of audio data corresponding to a link source video object which links to a plurality of link destination video objects and adds the cut blocks to the start of other pieces of audio data which correspond to the plurality of link destination video objects. This performs a process for preventing the reproduction of video data from delaying. As a result, even if a video object links to another video object, the reproduction of video data is not delayed.
In the above bitstream generation apparatus, the correcting means may include: a third correcting unit for cutting one or more blocks located at the start of each piece of video and audio data corresponding to a link destination video object which is linked from a plurality of link source video objects and adding the cut blocks to the end of other pieces of video and audio data which correspond to the plurality of link source video objects; and a fourth correcting unit for cutting one or more blocks located at the end of a plurality of pieces of audio data which correspond to the plurality of link source video objects and have been corrected by the third correcting unit and adding the cut blocks to the start of another piece of audio data which corresponds to the link destination video object and has been corrected by the third correcting unit.
With the above arrangement, the third and fourth correcting units perform correction processes even when the link setting unit sets relation of a plurality of link-source video objects to a link-destination video object. This performs a process for preventing the reproduction of video data from delaying. As a result, even if a video object links to another video object, the reproduction of video data is not delayed.
In the above bitstream generation apparatus, each of the plurality of pieces of audio data obtained by the audio encoder uniquely may include a reproduction start time and a reproduction end time, the limitation imposed on each of the plurality of video objects dependent on the reproduction order may be a limitation required to allow the reproduction apparatus to change, in reproduction, from one video object to a next video object, keeping a synchronization of a video display with an audio output, and the correcting means may include an adjusting unit for, based on a reproduction end time of a piece of audio data corresponding to a video object, adjusting a reproduction start time of a piece of audio data corresponding to a next video object.
With the above construction, the synchronization between the video and audio reproduction is kept even if the reproduction order of the VOBs in the exclusive reproduction block is changed after the elementary streams are generated.